1. Field of the Invention
The present invention relates to a tire vulcanizing apparatus for molding and vulcanizing a green tire.
2. Description of the Related Art
In manufacture of tires, a tire vulcanizing apparatus using a self-locking container has been known as an apparatus for molding and vulcanizing a green tire. Such a tire vulcanizing apparatus is disclosed in, for example, Japanese Patent Publication No. 2505675 and Japanese Patent Application Publication No. 2001-79850.
As are described in these publications, in such a tire vulcanizing apparatus using a self-locking container, the self-locking container is a die container (a metal mold apparatus). The die container is a part for molding a tire, and basically includes an upper circular plate (a top plate), a lower circular plate (a lower plate), segments and an outer ring (a jacket). The upper circular plate and the lower circular plate retain an upper sidewall die (a metal mold) and a lower sidewall die (a metal mold), respectively. The upper sidewall die and the lower sidewall die are used for forming sidewall portions of a tire. The segments are separated from one another as plural sections, and retain tread dies (metal molds), respectively. The tread dies are used for forming a tread portion of a tire. The outer ring engages with the segments with their inclined surfaces being contact, and causes the segments to move in a radial direction thereof.
In the tire vulcanizing apparatus as described above, the die container is formed on a fixed base. The fixed base is a component member of a main body of the tire vulcanizing apparatus (hereinafter, referred to as an apparatus main body). The lower circular plate, to which the lower sidewall die is attached, is fixed to the base. The apparatus main body is provided with an elevating mechanism. In the elevating mechanism parts of the die container are elevated and lowered by means of a bolster plate, except a part corresponding to the lower circular plate. The elevating mechanism contributes also to the closing of the segments by lowering the outer ring. This elevating mechanism is provided with a mold opening/closing cylinder for opening and closing the segments. This mold opening/closing cylinder is joined to the upper circular plate, and upward and downward movements thereof cause the segment to open and close, respectively.
When a tire is caused to undergo vulcanization molding, the following is performed. A green tire is set in a mold formed of the upper sidewall die, the lower sidewall die and the tread dies. A bladder is inserted into the inner side of the green tire, and is brought into intimate contact with the green tire. Then a pressurizing/heating medium is introduced into the bladder. By introducing the pressurizing/heating medium into the bladder, the green tire is pressed against the inner surfaces of the upper and lower sidewall dies and the tread dies, by the pressurizing/heating medium contained in the bladder. The tire is formed through the vulcanization molding by maintaining this state for a predetermined length of time.
When the tire is pressurized and heated to be vulcanized, forces act on the tire in directions in which the upper and lower sidewall dies open. The forces are caused by the pressurizing/heating medium contained in the bladder introduced into the inner side of the tire. However, the upper and lower sidewall dies do not open because each of the upper and lower circular plates is held by lug portions on the segment side. Additionally, forces are generated also in directions in which the tread dies are radially expanded, and are constrained by the outer ring. Although component forces thereof act to push up the outer ring, these forces are relatively small. Accordingly, the closed state of the mold is maintained, for example, by retaining the outer ring with a cylinder. Note that a die clamping mechanism for a self-locking container is disclosed in, for example, Japanese Patent Publication No. 2505675 and the like, and that another one for others is disclosed in, for example, Japanese Patent Application Publication No. Hei10-138250 and the like.
In the tire vulcanizing apparatus as described above, for precisely molding a tire, the upper and lower sidewall dies and the tread dies should be precisely maintained in a closed state. The upper and lower sidewall dies are restrained respectively by having the lower and upper circular plates retained by the lug portions of the segments. Accordingly, it is necessary to machine, with high precision, abutting portions (contact portions) of the lug portions with the lower and upper circular plates. For this reason, there has been a problem that large amounts of time and labor are required for machining of the segments and the upper and lower circular plates. Additionally, there has been a problem that wear and the like of these abutting portions make it impossible to secure the precision.